Blurred version and other weird eye problems are common complaints among astronauts who have just got back to Earth after a recent trip to outer space. NASA's Scott Kelly is one of them.

A new study sheds light on the issue. Presented last November 28 at the annual meeting of the Radiological Society of North America (RSNA), the study revealed that visual problem affecting astronauts who serve on lengthy missions in space is related to volume changes in the clear fluid that is found around the brain and spinal cord.

"People initially didn't know what to make of it, and by 2010 there was growing concern as it became apparent that some of the astronauts had severe structural changes that were not fully reversible upon return to earth," said the study lead author Noam Alperin, Ph.D., professor of radiology and biomedical engineering at the University of Miami Miller School of Medicine in Miami, Florida, the Daily Mail writes.

In an article by Eureka Alert, the syndrome, known as visual impairment intracranial pressure (VIIP), was reported in nearly two-thirds of astronauts after long-duration missions aboard the International Space Station (ISS).

According to the study, scientists initially thought that the reason behind astronauts' vision problem was a shift of vascular fluid toward the upper body that occurs when astronauts spend time in the microgravity of space. However, Dr. Alperin's team probed another possible source for the problem: cerebrospinal fluid (CSF), the clear fluid that helps cushion the brain and spinal cord while circulating nutrients and removing waste materials.

"On earth, the CSF system is built to accommodate these pressure changes, but in space the system is confused by the lack of the posture-related pressure changes.The research provides, for the first time, quantitative evidence obtained from short- and long-duration astronauts pointing to the primary and direct role of the CSF in the globe deformations seen in astronauts with visual impairment syndrome," Dr. Alperin added.

Emphasizing its importance, he warned that if the ocular structural deformations are not identified early, astronauts could suffer irreversible damage. As the eye globe becomes more flattened, the astronauts become hyperopic, or far-sighted. Dr. Alperin mentioned NASA is already looking into several possible measures to simulate the conditions that lead to VIIP and testing various countermeasures.